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NQOISC (Not Quite One Instruction Set Computer)

This repository contains the source code for the NQOISC basic toolchain. The C compiler is contained in it's own repository here.

The NQOISC Instruction Set

The insruction set is based on brainfuck. Each instruction is 32-bits long. Memory is byte addressed and uses big endian. There are two registers a program counter and a data pointer. The data pointer points to the current memory address to be modified and the program counter points to the next instruction to be executed. It is assumed that both the program counter and the data pointer are initialized to zero.

Any I/O is memory mapped.

Instruction format:

Opcode  Imm 30-bit
00      000000000000000000000000000000

Note: Imm is sign extended to 32-bits.

Opcode Name Description
00 right imm Move the data pointer to the right by imm bytes.
01 add imm Add imm to the current address pointed to by the data pointer.
10 bnz imm Set the program counter to program counter + imm if the current address pointed to by the data pointer is equal to zero.

Compiling

Run this command to compile the toolchain.

# ./build.sh && ./install.sh

Files

Name Description
disassembler.c NQOISC disassembler.
simulator.c ISA simulator. Run nqoisc-sim -h for more info.
asm.c An assembler.
build.sh Bash script to build the toolchain.
install.sh Bash script to install the toolchain.
vector.h Header file for vector.c.
vector.c A simple vector implementation.

Using the tools

The Disassembler

To disassemble an NQOISC binary run the following command.

nqoisc-disassembler binary.bin

The Simulator

Run nqoisc-sim -h for info on how to use the simulator.

The assembler

Run nqoisc-asm -h for instructions on how to use the command.

Assembly language EBNF.

program ::= stmt.
program ::= program stmt.

stmt ::= instruction-stmt.
stmt ::= label-stmt.

label-stmt ::= ? Identifier followed by a colon ?.
instruction-stmt ::= instruction value.

value ::= INTEGER.
value ::= IDENTIFIER.
value ::= PROGRAM_SIZE.

instruction ::= RIGHT.
instruction ::= LEFT.
instruction ::= ADD.
instruction ::= SUB.
instruction ::= BNZ.
Instruction Description Is a pseudo instruction?
right x Move the data pointer right. No.
left x Move the data pointer left. right -x
add x Add x to the value under the data pointer. No.
sub x Subtract x from the value under the data pointer. add -x
bnz label Branch if the value under the data pointer is not zero No.